It looks like an aftermarket Professional Products 75mm throttle body.
http://www.ebay.com/itm/like/231784321914?lpid=82&chn=ps&ul_noapp=true
Yep, 75mm ID.
There have been machining problems with some, but if your car is running good, I wouldn't worry about it.
I used one for 4-5 years.
Might check to see if the inlet was opened up a little bit to make the TB to inlet transition a smooth one. I bought a car awhile back that someone just slapped the TB on there without doing anything to the inlet.
Despite me responding so late, whoever did this mod, did what you said. Just slapped it on. So I guess I should do something about that.